Chapter 6 The States of Matter 6.3-6.5 The Solid, Liquid, & Gaseous States

Kinetic Theory of Solids A solid consists of large number of particles that: High density. The particles of solids are located as closely together as possible. Therefore, large number of particles are contained in a small volume, resulting in a high density. Definite shape. The strong cohesive forces hold the particles of solids in essentially fixed positions, resulting in a definite shape. Small compressibility. Because there is very little space between particle of solids, increased pressure cannot push them closer together, and it will have little effect on the volume.

Kinetic Theory of Solids (cont.) A solid consists of large number of particles that: Very small thermal expansion. Increased temperature increases the vibrational motion of the particles and the disruptive forces acting on them. Each particle vibrates with an increased amplitude and “occupies” a slightly large volume. However, there is only a slight expansion of the solid because the strong cohesive forces prevent this effect from becoming very large.

Kinetic Theory of Liquids A liquid consists of large number of particles that: High density. The particles of liquids are not widely separated; they essentially touch each other. There will, therefore, be a large number of particles per unit volume and a high density. Indefinite shape. Although not completely independent of each other, the particles in a liquid are free to move over and around each other in a random manner, limited only by the containers walls and the extent to which the container is filled. Small compressibility. Because the particles in a liquid essentially touch each other, there is very little space between them. Therefore, increased pressure cannot squeeze the particles much more closely together.

Kinetic Theory of Solids (cont.) A liquid consists of large number of particles that: Small thermal expansion. Most of the particle movement in a liquid is vibrational because the particles can move only a short distance before colliding with a neighbor. Therefore, the increased particle velocity that accompanies a temperature increase results only in increased vibration. The net effect is that the particles push away from each other a little more, thereby causing a slight volume increase in the liquid.

Kinetic Theory of Gases A gas consists of small number particles that: Low density. The particles of a gas are widely separated. There a relatively few of them in a given volume, which means there is little mass per unit volume. Indefinite shape. The forces of attraction between particles have been overcome by kinetic energy, and the particles are free to travel in all directions. Large compressibility. The gas particles are widely separated, so that a gas sample is mostly empty space. When pressure is applied, the particles are easily pushed closer together, decreasing the amount of empty space and the gas volume.

Kinetic Theory of Gases (cont.) A gas consists of small number particles that Moderate thermal expansion. Gas particles move in straight lines except when they collide with each other or with container walls. Thus, they push each other away more strongly, and at constant pressure this causes the gas itself to occupy a significant larger volume.

Kinetic Molecular View of Matter (b) (c) (a) Solid state: The particles are close together and held in fixed positions; they do not need a container (b) Liquid state: The particles are close together but not held in fixed positions; they take the shape of the container. (c) Gaseous state: The particles are far apart and completely fill the container.